1. Field of the Invention
The present invention relates to a display lamp using LEDs as a light source and arranged to diffuse and emit lights efficiently from the inside of a globe serving as a display portion.
2. Description of Related Art
As a display lamp such as a signal informing display lamp or the like, a display lamp using LEDs as a light source is conventionally widely used at a factory production line, a variety of entrances and exits for which attention should be called, a construction site or the like. Such a display lamp does not require frequent change of a bulb as done with a conventional incandescent lamp source, and is resistant against external factors such as vibration and the like.
As an example of the display lamp of this type, there is a display lamp having a display portion to be installed on a wall face and arranged to emit light forward or obliquely forward of the wall face.
For example, in a display lamp 90 shown in FIG. 13, a globe 92 having an arcuate section covers the front of a flat-type rear plate 91 of a case to be attached onto a wall face. A plurality of LEDs 94 are arranged on a substrate 93 attached, in parallel, to the rear plate 91. Each of the LEDs 94 irradiates light toward the zone just in front of the globe 92
On the other hand, a display lamp 90 shown in FIG. 14 uses a substrate 93 made in the form of a curve similar to that of a globe 92. Each of LEDs 94 irradiates light radially in the normal-line direction of the globe 92, i.e., toward the zone in close vicinity to the globe 92.
The display lamp 90 in each of FIGS. 13 and 14 has a short distance between each LED 94 and the zone to be irradiated of the globe 92 (equivalent to the optical path length between the light emission of each LED 94 and the light irradiation onto the globe 92). Particularly, in the arrangement in FIG. 14, the distance between the substrate 93 and the globe 92 is short and the optical path length above-mentioned is therefore particularly short.
When the optical path length is short, the light from each LED 94 cannot sufficiently be diffused before the light reaches the globe 92. This narrows that zone of the globe 92 to be illuminated by each LED 94. Accordingly, to irradiate light to the globe 92 in its entirety to improve the visibility, it is required to use a number of LEDs 94.
It is an object of the present invention to provide a display lamp arranged to efficiently utilize the lights from LEDs, enabling the number of the LEDs to be reduced, yet assuring the visibility.
The present invention provides a display lamp in which the front face of a plane non-display portion is surrounded by a globe, as a display portion, vertically extending and having an arcuate cross section or a polygonal cross section when combined with the non-display portion, and in which a light source is disposed inside of the space defined by the globe and the non-display portion. In the display lamp according to the present invention, the light source comprises at least a pair of left and right LEDs disposed at both sides which sandwich the transverse center of the front face of the non-display portion. These LEDs respectively irradiate lights to those zones of the globe which are located in the opposite sides with respect to the LEDs on the basis of the transverse center of the globe.
According to the arrangement above-mentioned, for example the LED disposed at the left side irradiates light toward the zone at the right side of the globe. Accordingly, a long distance can readily be assured as the distance required for light diffusion. This results in expansion of the area of the globe zone to be irradiated by the light from each LED. It is therefore possible to illuminate the whole globe with the number of LEDs reduced.
The at least a pair of left and right LEDs may comprise a pair of left- and right-side end LEDs disposed at the left and right ends or their vicinities of the front face of the non-display portion. Preferably, the pair of left- and right-side end LEDs respectively irradiate lights to those parts of the globe which are respectively opposite to the right- and left-side end LEDs as separated from each other with the largest distance provided therebetween. According to the arrangement above-mentioned, the distance required for diffusion of the light from each end LED can securely be maximized.
Preferably, the light source comprises a center LED which is disposed at the transverse center of the non-display portion and which irradiates light to the transverse center and its vicinity of the globe.
The lights from the end LEDs are generally directed to the peripheral edge parts of the globe. Accordingly, there are instances where the amount of light to be irradiated to the globe center is insufficient. In this connection, when the center LED is disposed, the light can sufficiently be irradiated to the center and its vicinity of the globe.
Instead of the center LED, or in addition to the center LED, there may be disposed reflection means for reflecting portions of the lights from the pair of left and right LEDs to the transverse center and its vicinity of the globe. According to the arrangement above-mentioned, the reflection means can sufficiently irradiate such light portions to the transverse center and its vicinity of the globe. When the reflection means is disposed instead of the center LED, the number of the LEDs can further be reduced.
There may be disposed, on the non-display portion, reflection means for reflecting portions of the lights from the pair of left and right LEDs toward those zones of the globe which are located in the same sides with respect to the LEDs in the transverse direction.
According to the arrangement above-mentioned, the lights from the LEDs are irradiated to the zones which are located not only in the opposite sides, but also in the same sides. Further, because the optical paths can be bent by reflection, there can be provided such optical path lengths as to assure sufficient light diffusion. As a result, even in the case of light irradiation to the zones at the same sides, the irradiation area can be expanded. This results in further expansion of the area to be irradiated by the light from each LED.
The reflection means may be formed by the surface of a portion of a case which supports the globe. According to this arrangement, the integration of the reflection means with a portion of the case can simplify the structure of the display lamp. Further, because such integration eliminates the labor of assembling the reflection means with the case, the assembling is facilitated.
The case may comprise a pair of end members which hold the upper and lower ends of the globe, and a post member which connects the pair of end members to each other. In this case, the reflection means is preferably formed on a surface of this post member. According to this arrangement, the post member can reinforce the connection of the end members to each other, and the structure can be simplified in that the reflection means is formed on a surface of the post member.